ELFT HÍRADÓ

[Janos Asboth <asboth.janos AT wigner.mta.hu>]

Kedves Munkatársak!

Egy érdekes szemináriumra szeretném felhívni a figyelmeteket - ugyan a
fizinfóra kiment, de talán nem árt emlékeztetni. A héten pénteken Andreas
Schnyder, a "topologikus szigetelők periodusos rendszerének" egyik
megalkotója tart egy szemináriumot a BME Elméleti Fizika Tanszékén.

Üdv,
 Asbóth János


                          Andreas Schnyder
                           (MPI Stuttgart)


          Three-dimensional topological Dirac materials


Although topologically nontrivial properties are normally associated with
insulating phases, recent developments have shown that (semi)metallic
phases can also be topological. In this talk, I will survey recent
developments regarding the topological classifications of (semi)metallic
materials in terms of crystal symmetries [1,2]. As a concrete examples, I
will present results about the recently discovered compound Ca3P2 [3],
which has a line of Dirac nodes near the Fermi energy. I will discuss the
topological properties of Ca3P2 in terms of a low-energy effective theory
and a tight-binding model, derived from ab initio DFT calculations. The
microscopic model for Ca3P2 shows that the drumhead surface states have a
rather weak dispersion, which implies that correlation effects are enhanced
at the surface of Ca3P2. Furthermore, I will discuss the parity anomaly
that exists in this nodal-line semimetal and show how it is connected to
unusual transport phenomena. If time permits, I will also survey the
topological properties of the Dirac materials A3EO [4], where A denotes an
alkaline earth metal, while E stands for Pb or Sn. I will discuss the
magnetic properties of this Dirac system and show that a strong Zeeman
field splits the gapped Dirac cones into ungapped Weyl points, which are
protected by a quantized Chern number.


[1] Ching-Kai Chiu, Andreas P. Schnyder, Phys. Rev. B 90, 205136 (2014).
[2] Y. X. Zhao, Andreas P. Schnyder, Z. D. Wang, Phys. Rev. Lett. 116,
156402 (2016).
[3] Y.-H. Chan, Ching-Kai Chiu, M. Y. Chou, A. P. Schnyder, Phys. Rev. B
93, 205132 (2016).
[4] Ching-Kai Chiu, Y.-H. Chan, Xiao Li, Y. Nohara, A. P. Schnyder ,
arXiv:1606.03456 (submitted).


Időpont: 2016. szeptember 9. péntek, 10:15
Helyszín: BME Fizikai Intézet, Elméleti Fizika Tanszék,
Budafoki út 8. F-épület, III lépcsőház, szemináriumi szoba